Filtration devices are frequently employed in laboratory and other environments to remove solids from a liquid sample. Liquid samples, for example, biological samples such as blood and urine, may be filtered to remove particulate matter such as contaminants or unwanted protein. The filtrate may then be used to perform laboratory tests, such as high-performance liquid chromatography (HPLC) analysis.
Some laboratory filtration devices, typically referred to as “syringe filters”, include a standard laboratory syringe, into which a liquid sample to be filtered is drawn. A syringe filter is then fitted to the tip of the syringe and the syringe plunger is compressed, forcing the liquid sample contained within through the syringe filter into a separate receptacle. However, use of syringe filters according to the above procedure can be time consuming, and due to the number of components required, can be relatively costly.
Alternative laboratory filtration devices, referred to as “syringeless filters”, in which no syringe is used have been developed, such as the Whatman™ Mini-Uniprep™. FIG. 1 shows an exemplary syringeless filter device 100, in assembled form. The device 100 comprises a vial 102 (typically having a capacity of approximately 0.4 ml) for holding a liquid sample 104 to be filtered. The device 100 also comprises a hollow plunger 106 having a filtration membrane 108 at one end, and a pre-attached cap 110 at the other end. During filtration, the device 100 is compressed so that the plunger 106 slides towards the bottom of the vial 102; as the plunger 106 slides, a seal 112 on the exterior walls of the plunger 106 engages with the internal walls of the vial 102, preventing the liquid sample 104 from passing around the outside of the plunger 106. Accordingly, the liquid sample 104 is forced through the filtration membrane 108, and into the interior of the plunger 106 where it collects as a filtrate 114, leaving filtered particles in the bottom of the vial 102. Vents 116 in the body of the plunger 106 allow air to escape as the plunger 106 fills. When the device 100 is fully compressed, a locking ring 118 engages with the inner wall of the vial 102 to form an air-tight seal. The filtrate 114 can then be stored or transported in this state for extended periods (typically up to several days) until it is needed, at which time it may be removed from the plunger by, for example, using a syringe needle to pierce a septa seal 120 in the cap 110.
Whilst the term “syringeless filter device” is used herein, an alternative term often used is “filter vial”, as in the case of the Thomson SINGLE StEP™ Filter Vial device; such devices perform the same function as the syringeless filter device described above and may be operated in the same way.
Syringeless filter devices such as those described above are simpler to use than syringe filters, and typically have fewer parts, making them simpler to manufacture than syringe filters.
The step of compressing the syringeless filter device may be performed manually, with a human operator pressing the plunger into the vial using their hand. However, this may be time consuming, and can be uncomfortable for the operator, since the force required to push the plunger into the vial may be significant, due to the sealing contact described above. Further, the compression process can result in breakage of the syringeless filter device, especially where glass components are used, and leakage of the sample. This poses a risk of injury to the operator, as well as potentially bringing him or her into contact with the sample to be filtered; in particular, where the sample is held in a potentially harmful solvent such as acetonitrile or methanol, such contact is undesirable.
The Whatman™ Six Position Compressor™ is a device for compressing multiple syringeless filter devices in a single action. The device comprises a base fixed to a hand lever via a pivot. The base includes six shallow recesses, arranged in a straight line, for locating syringeless filter devices for compression. In use, the hand lever is raised to allow an operator to individually locate each of the uncompressed syringeless filter devices in the recesses. The operator then brings down the hand lever to a horizontal position, and the lever pushes downwards onto each of the syringeless filter devices, and compresses them, in turn.
It is an object of the present invention to provide an improved syringeless filter device compressor.